1. Field of the invention:
The invention relates to a supporting frame for a platform, balcony, stairs or the like and more particularly to a prefabricated stair kit. It includes a pair of grooved stringers and a set of support blocks slidingly fitted in the groove of the stringers for supporting the treads of the stairs.
2. Prior Art:
U.S. Pat. No. 2,021,457 is directed to a stair carriage made of grooved stringers and a set of blocks each connected to the stringers by a spline or a tongue. The groove of the stringer is adapted to receive only the spline or the tongue. Considering the limited degree of precision in making these parts, a gap is quite often likely to appear at the intersection of the stringer and support block. Furthermore, and as explained in the above mentioned patent, spacers are needed when the block do not have the desired dimensions. The use of such spacers causes an opening between the upper edge of the riser and the bottom of the tread. To hide this opening, a molding strip is used. When the stringers are not quite at the same angle relative to the ground or for some similar reasons, it is useful to be able to vertically raise the blocks without the use of the spacers. Such modification cannot be made because the spline and the tongue mentioned above cannot be adjusted.
It is an object of the present invention to overcome the above described disadvantages.